The invention is based on a process for joining component workpieces.
Among the processes for joining components made of high-temperature materials the welding and bonding processes employing diffusion occupy a leading position. Diffusion bonding without additional material, a type of pressure welding below the solidus line of the materials to be joined is known (R. Brunetaud, D. Coutsouradis, T. B. Gibbons, Y. Lindblom, D. B. Meadowcroft, R. Stickler, High Temperature Alloys for Gas Turbines 1982, D. Reidel Publishing Company, Dordrecht, Holland/Boston, U.S.A./London, England, in particular Diffusion Bonding of Superalloys for Gas Turbines, pages 1,043-1,050). On the other hand joining processes of a similar type employing additional material in the form of one or more intermediate layers have also been proposed (Hanno Brenninghoff, "Diffusionsschweissen, Verfahren, Anwendungen, Werkstoffe, Prufen" ("Diffusion Welding, Processes, Applications, Materials, Testing"), DVS (German Welding Technique Association) Report 69 on International Colloquium entitled "Brazing and High-Temperature Soldering and Diffusion Welding", Essen, 21/22.9.1981, reprinted in Technische Rundschau No. 5, Feb. 2, 1982).
In view of the high costs and the risk in using conventional welding techniques (build-up welding) suitable brazing techniques have been proposed and developed for repairing damaged or worn turbine blades made of super-alloys. These also employ among other things additional materials in powder form (cf. the work cited above entitled High Temperature Alloys for Gas Turbines 1982, in particular the chapter entitled Blade Repair and Recovery, pages 931-954, especially "Repair Brazing of Superalloy Gas Turbine Components, pages 945-950).
In the case of conventional diffusion bonding it is essential that the surfaces of the component workpieces to be bonded are very precisely processed and as a rule are flat surfaces. This is the only way of guaranteeing a monolithic product in which there is not intermediate zone and a subsequent heat treatment (e.g. coarse-grain annealing) can be guaranteed to be completely successful over the entire cross-section of the workpiece. The process is therefore expensive and time-consuming and allows the designer only limited freedome in shaping the workpiece. In the case of brazing, on the other hand, intermediate zones are always encountered which have a texture differing from that of the basic material. In addition there is a danger of pore formation in these transition and intermediate layers with all the adverse effects this has on the formation of texture. There can therefore be no possibility of the products being monolithic.
There is a considerable requirement for improving the known processes to overcome the difficulties mentioned above as well as possible.